The present invention relates to an eyeglass lens processing apparatus which processes an eyeglass lens.
In an eyeglass lens processing apparatus, an eyeglass lens is rotated while being held (chucked) by two lens chucks, and the periphery of the lens is processed by a processing tool such as a grindstone so as to substantially conform to a desired target lens shape. The chucking of the lens is performed by fixedly attaching a cup serving as a fixture to the rear refractive surface of the lens by suction, adhesion, or the like, mounting the cup to which the lens is fixed to a cup receiver at a distal end of the one lens chuck, and allowing a lens presser at a distal end of the other lens chuck to abut on the lens.
When the periphery of the lens is processed with the processing tool which rotates at high speed, if a load exceeding the holding (chucking) force of the lens is applied to the lens, axis deviation in a rotation direction may occur between the cup and the lens. In particular, in a liquid-repellent lens whose front refractive surface and rear refractive surface (hereinafter, simply refer to surface) are coated with a liquid-repellant substance to which water, oil, or the like does not stick easily, the possibility of occurrence of axis deviation in the rotation direction is high because the surface slips readily.
It has been assumed that large (high) chucking pressure of the lens chucks suppresses the occurrence of axis deviation in the rotation direction when the lens having the surface slipping readily is processed. However, when the chucking pressure is large (high), axis deviation occurs between the cup and the lens in a lateral (transverse) direction perpendicular to the central axis of rotation of the lens chucks due to the curve of the surface of the lens. For example, as shown in FIG. 8, when the central axis Lx of rotation of two lens chucks 702L and 702R is not aligned with the optical center Lo of the lens and the lens is chucked by the lens chucks 702L and 702R, if the chucking pressure is high, the lateral axis deviation occurs in a direction in which the edge at the chucked portion is thicker.